The Convention Against Torture, which President Reagan signed 25 years ago, states "[n]o exceptional circumstances whatsoever, whether a state of war or a threat of war, internal political instability or any other public emergency, may be invoked as a justification of torture." Reagan would be disappointed many Americans reject that view.

In a recent poll, only 25 percent of Americans said the use of torture against suspected terrorists was "never justified," while a combined 47 percent said it was "always" or "sometimes justified." Public support for torture is surely based on the well-publicized claims that brutal interrogations were necessary to defeat al Qaeda and prevent future terrorist attacks.

As a former Army intelligence officer who taught prisoner-of-war interrogation for 18 years, I am skeptical of those claims. But, given how much evidence about the CIA program remains classified, I understand the public's confusion.

Even CIA director John Brennan recently expressed uncertainty about the interrogation program's efficacy. In 2007, he said the program "saved lives." But during his recent Senate confirmation hearing, he said reading the Senate Intelligence Committee's classified report on the program "raises questions about the information that I was given at the time . . . at this point, Senator, I do not know what the truth is."

The Constitution Project's Task Force on Detainee Treatment, of which I am a member, conducted a two-year study of treatment of counterterrorism detainees, and found serious flaws with many of the claims defenders have made about torture's efficacy.

For example, in the days after Osama Bin Laden's death, former Attorney General Michael Mukasey claimed 9/11 mastermind Khalid Sheikh Mohammed (KSM) "broke like a dam" after being waterboarded and gave investigators the nickname of a bin Laden trusted courier. It later became apparent this was untrue.

A month after the Abbottabad raid, former CIA director Michael Hayden acknowledged KSM had never revealed the courier's name or alias, but wrote "it is nearly impossible to imagine" how bin Laden could have been killed without intelligence gained from the CIA program. Senators Dianne Feinstein and Carl Levin, chairs of the Senate committees on Intelligence and Armed Services, said the Senate Intelligence Committee investigation showed Hayden was "wrong," and the original information on the bin Laden courier "had no connection to CIA detainees."

Torture defenders often cite a plot to crash planes into Los Angeles' highest skyscraper, the 73-story Library Tower, as an example of a "ticking time bomb" allegedly defused by the CIA torture program. Marc Thiessen has written that "without enhanced interrogations, there could be a hole in the ground in Los Angeles to match the one in New York." The Justice Department's Office of Legal Counsel repeatedly cited supposed revelations from detainees about this plot in concluding that the CIA program was effective.

KSM was, in fact, involved in a plot to crash hijacked planes into a skyscraper in Los Angeles, using a cell of Southeast Asian hijackers. But the terrorist cell's leader, Masran bin Arshad, confessed many details of the plot after his detention by Malaysian intelligence in February 2002 -- long before KSM was captured in March 2003. Two other cell members were captured after KSM, but it is unclear what role CIA detainees' revelations had in their detention, and in any case there is no good evidence the Los Angeles plot was reactivated after Arshad's arrest.

KSM's and two other CIA detainees' interrogations in 2003 did not stop a "ticking bomb" plot all three had allegedly been involved in financing. On August 5, 2003, a suicide bomber detonated a truck bomb outside the lobby of the Jakarta Marriott Hotel, killing 11 people and wounding at least 81. But the attacks torture failed to prevent are too often overlooked in this debate -- as are the false confessions, the terrorists recruited, and the witnesses who do not report their suspicions as a result of torture.

The officials, beginning with former President Bush and Vice President Cheney, who authorized the CIA's brutal treatment of prisoners, have an obvious motivation to argue the program saved lives. One would expect them to push for full public disclosure of evidence of these successes. If such evidence exists, the public deserves to see it.

But if -- as I believe -- the evidence does not exist, the public deserves to know that as well. More than a decade after 9/11, "trust us" is no longer a sufficient response.

David Irvine is a retired brigadier general of the U.S. Army, a former state legislator, and a Salt Lake City attorney in private practice.